This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Breast milk is considered the nutrition of choice for infants, including premature infants in the Neonatal ICU (NICU). In the case of very low birth weight (VLBW) infants, this milk is generally supplemented with a human milk fortifier (HMF) in order to provide the additional nutrients that these babies require. We propose to investigate a HMF made from pasteurized donor human milk, in particular regarding calcium absorption, growth, bone mineral status, body composition, and feeding tolerance. We hypothesize that these study parameters will result in adequate outcomes with the use of the donor milk based HMF. The use of a human milk fortifier made from pasteurized donor human milk will provide adequate calcium absorption to preterm infants. In addition, this new fortifier will provide adequate growth and bone mineralization. SPECIFIC AIMS: Primary Aim: To determine calcium absorption in premature infants fed mother's own milk fortified with pasteurized donor human milk fortifier. Secondary Aims: (1) To evaluate the growth, bone mineral status, and body composition of premature infants fed mother's own milk fortified with pasteurized donor human milk fortifier, and, (2) To assess feeding tolerance (pilot data) in infants fed mother's own milk fortified with pasteurized donor human milk. BACKGROUND AND SIGNIFICANCE:Infants who are premature and below about 2.0 kg have unique nutritional requirements including a need for higher intakes of protein and minerals on a body weight basis than full-term infants. Routine cow's milk based formula as well as mother's own milk are insufficient to meet those requirements. Therefore, virtually all infants <2.0 kg are fed either their own mother's milk fortified with a cow's milk based powdered infant fortifier or, if the mother does not proved an adequate volume of her milk or chooses not to breast feed, they will receive a cow's milk based formula designed for premature infants. Although these products have been used for many years and have been shown to be relatively safe and effective, persistent concerns exist regarding an increased risk of infections and necrotizing enterocolitis (NEC) in premature infants who receive cow's milk based feeding products. It has been shown that feeding tolerance is enhanced and NEC risk is decreased in infants receiving human milk, although the specific benefits of avoiding all cow's milk protein are uncertain. The possibility of safely and effectively avoiding the use of all cow's milk based products has recently become possible due to the development of a human milk-based fortifier made from pasteurized donor human milk (Prolact-plus, Prolacta Bioscience, Monrovia, CA). The effectiveness of this fortifier in preventing infections and NEC will be tested in a multi-center trial in 2007. To date, it has been used only in individual cases and in smaller growth trials. However, the biological equivalence of using this newer donor milk product is not known. Specifically, the appropriate level and bioavailability of calcium, which is critical for preterm infants has not been tested from a donor milk product such as the Prolact-Plus. Therefore, we are conducting this study to determine the calcium and bone mineral effects of this product, using a protocol similar to that which will be used in the upcoming multi-center efficacy trial.